The present invention is directed to a method for synchronizing base stations in a multicellular, wireless telephone system, whereby the base stations are connected to a communication system via trunk lines.
Such a multicellular, wireless telephone system is disclosed in German Patent Application P 43 09 848.7 (corresponding to U.S. Ser. No. 214,570, filed Mar. 18, 1994 and hereby incorporated by reference) and is disclosed in the publication Telcom Report 8 (1985), No. 5, "Die Basisstation im zellularen Funkfernsprechnetz C450". A communication system, particularly a telecommunication private branch exchange, is connected via trunk lines to the base stations. Digitized voice and signaling information to be communicated from or to the communication terminal equipment, that is wirelessly connected to the base stations, is transmitted via the trunk lines. A communication of the synchronization information via the trunk lines is possible for base stations connected to a communication system by trunk lines. Phase deviations in the processing clock signals arise in the communication due to different trunk line running times and different processing speeds of the synchronization equipment that are realized in circuit-oriented terms. As a result phase deviations occur in the wireless or broadcast signals which cause particular disturbances in the coverage areas of the neighboring base stations.
A method for wireless synchronization of base stations for the radio telephone network C450 is described in another publication, Telcom Report 9 (1986), Special Issue "Nachrichtenuebertragung auf Funkwegen, pages 286-288, "Netzsynchronitaet im Mobilfunksystem C450". In this method, all other base stations are arranged around an initial base station in concentric rings. The initial base station wirelessly synchronizes the base stations of the first ring. The base stations of the first ring synchronize the base stations of the second ring, etc. Disturbances of the neighboring coverage areas are likewise possible due to different running times or phase deviations, particularly in neighboring base stations of one ring that are allocated to a common reference base station.